Fix Create/Edit Challenge spacing issues

[gaitonde]

There are some spacing issues in the Create/Edit Challenge page. Example in the registration info section -

[bryceglass]

As a first step, I'll just catalog the issues here, before we decide whether or not to address them in version 0.1 (they may break some display logic in the Challenge Map.)

[bryceglass]

Moving to post-0.1 for now. Cosmetic issues, not functional.